An orchestra played $6$ concerts in a concert hall. $40$ tickets were sold for each concert. How many tickets were sold in all?
Solution: ${40}$ tickets is the same as ${4\text{ groups of ten}}$ tickets. There were $6$ concerts. Total number of tickets sold: $\begin{aligned}&6\times{4\text{ groups of ten}}\\ =&{24\text{ groups of ten}}\\ =&{240}\end{aligned}$ ${240}$ tickets were sold in all.